Non-chargeable electrodes for use in contaminated environment containing organic contaminants

ABSTRACT

Electrodes for establishing an electrostatic field to influence focus and deflection of an electron beam in a light valve have their surfaces which are exposed to the beam coated with chemically active, electrically conductive, sorbent materials in order to immediately sorb vapors which condense thereon. The electrodes are thus maintained uniformly conductive, precluding spurious charge buildup and facilitating precise control of the beam.

United States Patent 1191 Inventor: Patrick P. Coppola, Fayetteville,

Assignee: General Electric Company, Syracuse, NY.

Filed: Dec. 18, 1972 Appl. No.: 315,917

Related US. Application Data Continuation-impart of Ser. No. 833,001, June 13, 1969, abandoned.

U.S. c1. 313/178, 313/465 161. ci. 1101 1/48 Field of Search 178/7.5 D; 313/82, 178,

References Cited UNITED STATES PATENTS 1/1927 McCullough ..252/l8l.l 1/1954 Longini ..3l3/65 Coppola 1 Mar. 25, 1975 [54] NON-CHARGEABLE ELECTRODES FOR 3,275,748 9/1966 Knoll et al. 313/465 USE IN CONTAMINATED ENVIRONMENT 3,331,657 9/1967 Romano et al. l78/7.5 D

3,3 4,874 7/1968 Marshall 313/178 CONTAINING ORGANIC CONTAMINANTS 3,526,799 9/1970 Coppola 8113i. 313/448 OTHER PUBLICATIONS Benton, William, Publisher, Encyclopaedia Britannica Adsorption, Volume I, pp. 182-184, c. 1957, Encyclopaedia Britannica, Inc. Chicago; London; Toronto.

Primary Examiner-Ronald L. Wibert Assistant Examinew-Richard A. Rosenberger Attorney, Agent, or FirmMarvin Snyder [5 7] ABSTRACT Y Electrodes for establishing an electrostatic field to influence focus and deflection of an electron beam in a light valve have their surfaces which are exposed to the beam coated with chemically active, electrically conductive, sorbent materials in order to immediately sorb vapors which condense thereon. The electrodes are thus maintained uniformly conductive, precluding spurious charge buildup and facilitating precise control of the beam.

9 Claims, 2 Drawing Figures NON-CHARGEABLE ELECTRODES FOR USE IN CONTAMINATED ENVIRONMENT CONTAINING ORGANIC CONTAMINANTS This invention is a continuation in part of copending application Serial No. 833,001, filed June 13, 1969, now abandoned.

The invention relates to light valves, and more particularly to apparatus for extending the useful lifetime of electron beam control electrodes thereof.

One form oflight valve suitable for optical projection of electronically generated images onto a remote display surface comprises an evacuated envelope containing an electron gun in alignment with a transparent disk. The disk is rotated through a reservoir of light modulating fluid, typically of the polybenzyl toluene type, to deposit a continuously replenished layer of fluid on the disk surface. An electron beam of current controllable by a grid electrode is generated by the electron gun and passed through electrostatic beam deflecting and focusing means to a portion of the light modulating fluid layer so as to selectively deform the layer. The fluid deformations thus formed constitute diffraction gratings which, in conjunction with a Schlieren optical system, selectively control passage of light from a light source through the disk and through an output window in the light valve envelope in order to create visible images at a remote display surface on which the light impinges.

During light valve operation, the concentration of vapors of the light modulating fluid everywhere within the light valve is relatively large in comparison to the concentration during the quiescent light valve state. This is due in large measure to the elevated temperature (typically about 50C) of the fluid medium within the light valve during itsoperation, and the electron beam bombardment of the fluid layer. The fluid vapors thus emitted continuously condense on surfaces of the electrodes within the light valve and, as these vapors condense, they are continuously bombarded by electrons including both primary electrons from the electron beam and secondary emission electrons from surfaces bombarded by the primary electrons. Resistive coatings, comprised of either organic breakdown fragments of molecules of the fluid medium vapors or residues formed by bombardment of thin films of condensed fluid medium vapors by primary electrons and secondary emission electrons, are thus formed on the surfaces of the electrodes exposed to bombardment by these electrons. These surfaces typically include those of the focus and deflection electrodes of the light valve, which are operated at temperatures below lC. Once a resistive film of this type has been formed on an electrode, the electrode becomes susceptible of charge buildup thereon since there is no longer a conductive path for charge deposited thereon to be drawn away. The charge thus built up causes a perturbation in the path of the electron beam, thereby altering its characteristics in an uncontrollable, spurious manner. Consequently, there is a loss of precision in control of the electron beam', and operation of the light valve is thereby degraded.

The present invention makes use of chemically active, electrically conductive, sorbent materials to overcome the aforementioned loss of precise control over the electron beam characteristics. By coating materials of this type on' the major surfaces of the electrodes within the light valve, condensing vapors are immediately drawn into the porous structure of the sorbent material and chemically and physically combined therewith, so that the minute quantities of condensed vapors which would otherwise form highly resistive skins or films on the electrode surfaces are'not present thereon. The sorbent materials are further selected for their ability to consume considerable quantities of vapor while yet maintaining a high degree of electrical conductivity.

Accordingly, one object of'the invention is to provide electrodes for use in an evacuated environment containing organic vapor contaminants.

Another object is to provide, for use in a light valve; electrodes which remain electrically conductive for an extended length of time.

Another object of the invention is to provide electron beam deflection and focusing electrodes which tend to avoid buildup of electrical charge thereon.

Briefly, in accordance with a preferred embodiment of the invention, a light valve containing a layer of fluid deformable by impingement of. an electron beam thereon is provided. Means are provided within the light valve for producing an electron beam directed toward the fluid layer. A plurality of electrodes operating at temperatures below C are situated between the means producing the electron beam and the fluid layer in order to exert an electrical influence on the beam. Each of the electrodes comprises a metallic structure presenting a major surface toward the electron beam, and a chemically active, electrically conductive, sorbent material coated on the surface, the sorbent material having a rough-textured surface facing toward the electron beam.

BRIEF DESCRIPTION OF THE DRAWINGS The features of the invention believed to be novel are set forth with particularity in the appended claims. The invention itself, however, both as to orginization and method of operation, together with further objects and advantages. thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 is an isometric view of two sets of electrodes employing the instant invention, such as may be situated within a light valve; and

FIG..2 is a sectional view of a single electrode fabricated in accordance with the teachings of the instant invention. I

DESCRIPTION OF TYPICAL EMBODIMENTS Flg. 1 illustrates focus and deflection electrodes, such as employed in a light valve, fabricated according to the teachings of the instant invention. Electrodes 11 and 12 comprise a pair of vertical focus and deflection plates while electrodes 13 and 14 comprise a pair of horizontal focus and deflection plates. Similarly, electrodes I5 and 16 comprise a pair of vertical predeflection plates, while electrodes 17 and 18 comprise a pair of horizontal predeflection plates. The electrodes normally operate at, or a few degrees above, ambient temperature within the light valve, which ambient is above room temperature but below 100C.

Each of the aforementioned electrodes is energized through a respective lead 20, while the path of an electron beam is indicated generally by the dotted line 21, and is in the direction indicated by the arrows, A predeflection is imparted to the beam by the predeflection electrodes in the same direction as the main deflection, and is of suitable magnitude so that entry of the electron beam into the focusing field produced by electrodes ll, 12, 13 and 14 follows a shift in the center focus of the focusing field produced by the main deflection voltages. The predeflection thereby serves to avoid the deflection aberration which would otherwise occur as a result of the shift in center of focus arising as a result of combining the focus and deflection functions in one system of electrodes. An electron beam focus and deflection electrode system of this type is described and claimed in W. E. Glenn, Jr. US. Pat. No. 3,320,468, issued May 16, 1967, and assigned to the instant assignee.

Each of electrodes 1 ll 8, as well as other electrodes within the light valve if desired, such as electron beam centering plates for example, respectively contains a coating 22 of a chemically active, electrically conductive, sorbent material on its major surface presented toward the electron beam. Typically, the sorbent material comprises activated charcoal, although metal-layered zeolites may be employed in the alternative. Where activated charcoal is employed, the process for applying the charcoal to the metallic electrodes, which are typically comprised of nonmagnetic stainless steel, may be performed according to the following example.

EXAMPLE The following ingredients are placed in a one-quart porcelain ball mill to form a creamy slurry:

lOO grams charcoal (activated, finely ground) 135 cc Star brand sodium silicate, as a binder 35 cc deionized water.

The slurry is just covered with flint stones and is ground on rollers for 45 hours at 45-50 RPM.

After grinding, the ,mill is opened to add 150 cc of deionized water. The mill is then closed and rolled for an additional minutes, insuring proper dilution and rinsing the stones. The mixture is thereafter drained into a clean bottle. Immediately prior to use, the mixture is further rolled for at least 1 hour.

The electrodes are degreased by application of suitable organic solvents thereto, as by a rinse in acetone or isopropyl alcohol, and a hand brushed coating of the mixture is then applied to each. The electrodes thus coated are mounted in the light valve envelope and the envelope is evacuated of gas and sealed. The light valve is then baked at a temperature in the range of 200C to 400C for one to two hours, causing the coating to tenaciously adhere to the electrodes.

When the electrodes have been coated with activated charcoal in a manner such as described in the foregoing example, formation of resistive coatings thereon during light valve operation is discouraged. One reason for this beneficial result is that condensed vapors are immediately sorbed by the activated charcoal so that electrons cannot bombard minute quantities of condensed vapors and transform the condensed vapors into highly resistive skins or films on the electrodes surfaces. A second reason for the beneficial result is that the porous structure presents to the condensing vapors a large, irregular surface because of its rough texture. Accordingly a greatly extended period of time is required for an insulating film to build up with a sufficiently large surface area to acquire an electrical charge. Since the activated charcoal is itself electrically conductive, no charge buildup occurs directly on the charcoal. The net result is that the time required to build up a deleterious charge on the electrodes as a result of ions and electrons landing on insulating films atop the respective electrodes is greatly lengthened, thereby lenthening the useful lifetime of these electrodes. The distribution of activated charcoal coating 22 on electrode 11 is illustrated in section in FIG. 2.

The foregoing describes electrodes for use in an evacuated environment containing organic vapor contaminants. The electrodes are particularly adapted for use in a light valve inasmuch as they remain conductive for an extended length of time by discouraging formation of an insulating film thereon and consequent charge buildup due to ionic and electronic bombardment.

While only certain preferred features of the invention have been shown by way ofillustration, many modifications and changes will occur to those skilled in the art. For example, each of the electrodes may be formed in a manner respectively to include the sorbent material described herein as an integral part thereof. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

1 claim:

1. In a light valve containing a layer of organic fluid, said fluid being deformable by impingement of an electron beam thereon and evolving organic vapors when undergoing bombardment by electrons, and means producing an electron beam directed toward said layer of fluid, a plurality of electrodes for use at temperatures below C, said electrodes being situated between said means producing an electron beam and said layer of fluid in order to exert an electrical influence on said beam, each of said electrodes comprising:

a metallic structure presenting a major surface toward said electron beam; and

a chemically active, electrically conductive, sorbent material for said vapors covering at least a portion of said surface, said sorbent material having a rough-textured surface facing toward said electron beam to delay formation of a resistive film on said major surface.

2. The apparatus of claim 1 wherein said chemically active, electrically conductive, sorbent material comprises activated charcoal.

3. The apparatus of claim 1 including means coupled to each of said electrodes for applying electrical potentials thereto.

4. The apparatus of claim 2 including means coupled to each of said electrodes for applying electrical potentials thereto.

5. An electrode for use at temperatures below 100C in an enclosure containing electron beam producing means and being substantially evacuated of gas except for organic vapor contaminants therein, said electrode comprising:

a substrate layer presenting a major conductive surface toward said electron beam;

a layer of chemically active, electrically conductive, sorbent material for said vapor contaminants coated on said surface to delay formation'of a resistive film on said surface; and

means coupled to said layer of sorbent material for applying an electrical potential thereto.

6. The apparatus of claim 5 wherein said entire substrate layer is comprised of a conductive material, and

8. The apparatus of claim 5 wherein said substrate layer is comprised of nonmagnetic stainless steel, and further including conductive means coupled to said substrate layer for applying said electrical potential to said layer of sorbent materiaL 9. The apparatus ofclaim 8 wherein said layer of sorbent material comprises activated charcoal. 

1. IN A LIGHT VALVE CONTAINING A LAYER OF ORGANIC FLUID, SAID FLUID BEING DEFORMABLE BY IMPINGEMENT OF AN ELECTRON BEAM THEREON AND EVOLVING ORGANIC VAPORS WHEN UNDERGOING BOMBARDMENT BY ELECTRONS, AND MEANS PRODUCING AN ELECTRON BEAM DIRECTED TOWARD SAID LAYER OF FLUID, A PLURALITY OF ELECTRODES FOR USE AT TEMPERATURES BELOW 100*C, SAID ELECTRODES BEING SITUATED BETWEEN SAID MEANS PRODUCING AN ELECTRON BEAM AND SAID LAYER OF FLUID IN ORDER TO EXERT AN ELECTRICAL INFLUENCE ON SAID BEAM, EACH OF SAID ELECTRODES COMPRISING: A METALLIC STRUCTURE PRESENTING A MAJOR SURFACE TOWARD SAID ELECTRON BEAM; AND A CHEMICALLY ACTIVE, ELECTRICALLY CONDUCTIVE, SORBENT MATERIAL FOR SAID VAPORS COVERING AT LEAST A PORTION OF SAID SURFACE, SAID SORBENT MATERIAL HAVING A ROUGH-TEXTURED SURFACE FACING TOWARD SAID ELECTRON BEAM TO DELAY FORMATION OF A RESISTIVE FILM ON SAID MAJOR SURFACE.
 2. The apparatus of claim 1 wherein said chemically active, electrically conductive, sorbent material comprises activated charcoal.
 3. The apparatus of claim 1 including means coupled to each of said electrodes for applying electrical potentials thereto.
 4. The apparatus of claim 2 including means coupled to each of said electrodes for applying electrical potentials thereto.
 5. An electrode for use at temperatures below 100*C in an enclosure containing electron beam producing means and being substantially evacuated of gas except for organic vapor contaminants therein, said electrode comprising: a substrate layer presenting a major conductive surface toward said electron beam; a layer of chemically active, electrically conductive, sorbent material for said vapor contaminants coated on said surface to delay formation of a resistive film on said surface; and means coupled to said layer of sorbent material for applying an electrical potential thereto.
 6. The apparatus of claim 5 wherein said entire substrate layer is comprised of a conductive material, and further including conductive means coupled to said substrate layer for applying said electrical potential to said layer of sorbent material.
 7. The apparatus of claim 5 wherein said substrate layer is comprised of metal, and further including conductive means coupled to said substrate layer for applying said electrical potential to said layer of sorbent material.
 8. The apparatus of claim 5 wherein said substrate layer is comprised of nonmagnetic stainless steel, and further including conductive means coupled to said substrate layer for applying said electrical potential to said layer of sorbent material.
 9. The apparatus of claim 8 wherein said layer of sorbent material comprises activated charcoal. 